Rotating actuator

ABSTRACT

A rotating actuator includes a body and a shaft jointly defining at least one operating volume consisting of a an annular cavity compartmented by at least two partitions extending between two end surfaces of the cavity, one of the radial partitions being respectively borne by the shaft and the other by the body, and both partitions being provided on the opposite free edge thereof with a sealing element. The sealing element is extended in the direction of each end surface of the annular cavity up to each end surface, whereupon it extends into the connection area of the end surface and the body or, respectively, shaft. The sealing element is fitted is in the form of a continuous linear joint provided in kilometer length and can be cut up as it develops along one edge surface to another according to a loop-shaped trajectory.

This invention relates to a rotary actuator, preferably a hydraulicactuator.

It relates more particularly to a rotary actuator of the type composedof a body and a shaft delineating between one another at least oneworking volume, each working volume being composed of an annular cavitycompartmented by means of at least two partitions extending between twosurfaces, the so-called end surfaces of said cavity, one of these radialpartitions supported respectively by the shaft, the other by the body ofthe actuator, these radial partitions, by their free opposite edgeprovided with packing, coming into airtight, sliding support contact,one against the inside wall of the body, the other against the outsidewall of the shaft in such a way as to form at least two chambers ofvariable volume that are capable of being pressurized alternately byintake of a fluid to generate relative rotational displacement of thebody and the shaft.

Such an actuator is described more particularly in patentsFR-A-2,618,189 and DE-1,750,352. By virtue of their design, suchvane-type rotary actuators generally exhibit relatively rapid wear overtime due to the presence of leaks at the level of the seals or packingthat equip the section of each partition or vane. This wear is due torubbing and possible deformations of the components of the actuator. Itleads to the necessity of changing the packing relatively frequently.

When the seal is a preformed seal and is bonded at several locations, asshown in particular in FIGS. 3 and 4 of German Patent DE-1750,352, anyseal wear requires an identical seal to be kept in inventory forchanging it. Moreover, due to the pre-conforming, changing a seal is along and complex operation. In addition, the design of the seal thatequips the shaft of the actuator requires initiating connectionoperations in sensitive zones where there is a major risk of theconnection not lasting over time.

Moreover, as shown by patent FR-A-1,270,078 or GB-A-926,836, rotaryactuators are known in which the packing is compressed via a fluid inthe direction of the wall on which it is designed to be supported inorder to increase the effectiveness of sealing. However, due to theconfiguration of the seal, only the seal equipping the free edge of eachpartition can be pressurized. It is necessary to have an additional sealthat cannot be pressurized to achieve sealing in the connecting zonebetween the body and the shaft, at the level of the end surfaces of thebody. This again results in complexity of the assembly.

One objective of this invention is thus to propose a rotary actuator ofthe aforementioned type whose packing design is simplified especially tofacilitate installation and replacement of the packing without adverselyaffecting the sealing efficiency.

Another objective of this invention is to propose a rotary actuatorwhose packing design allows pressurization of all said packing, thispacking being capable, on the one hand, of ensuring a seal betweenchambers with a variable volume, and, on the other hand, the sealing ofsaid chambers to the outside.

Another objective of this invention is to propose a rotary actuatorwhose packing design makes it possible to limit the amount of packingnecessary.

Another objective of this invention is to propose a rotary actuatorwhose design allows implementation of an actuator of great length inwhich the risks of sagging of the shaft or buckling of the partitions orvanes are reduced or even eliminated.

To do this, the object of the invention is a rotary actuator of the typecomposed of a body and a shaft delineating between one another at leastone working volume, each working volume being composed of an annularcavity compartmented by at least two partitions extending between twosurfaces, the so-called end surfaces of said cavity, one of these radialpartitions supported respectively by the shaft, the other by the body ofthe actuator, the radial partitions by their free opposite edge equippedwith packing coming into airtight, sliding support contact, one againstthe inside wall of the body, the other against the outside wall of theshaft in such a way as to form at least two chambers of variable volumecapable of being pressurized alternately, by intake of a fluid, togenerate relative rotational displacement of the body and the shaft,characterized in that each packing that equips the free edge of apartition is lengthened in the direction of each end surface of theannular cavity just as far as said surface for extending into theconnecting zone between the end surface and the body or respectively theshaft, this packing that equips the shaft or body being present in theform of a continuous linear seal that is available by the kilometer andthat can be cut to length, for coming to rest in the groove of theactuator that is shaped depending on the desired arrangement of theseal, this seal developing from one end surface to the other following alooped trajectory, closing of the loop being obtained at least by theends of the strip comprising the seal being brought into contact.

Due to the configuration of the packing in the form of a continuouslinear seal extending from one end surface to the other as it passes thefree edge of the partition and develops in the form of a closed loop, itresults in the possibility of limiting the number of packings to two toobtain sealing between the chambers of variable volume and sealing tothe outside at the same time.

Moreover, due to this configuration, a double sealing barrier isobtained, especially in the zone extending along one free edge of apartition.

It is likewise possible, due to this configuration in the form of asimple seal strip, at the level of the path followed by the packing inthe groove arranged either in the body or in the shaft, to preventfolding of the seal at a right angle, folding that is recognized to beable to damage such a seal.

According to one preferred embodiment of the invention, the part of thepacking turned toward a part of the actuator such as the partition, bodyor shaft with which it is integral, is capable of being exposed duringoperation of the actuator to a thrust force that tends to keep theso-called active part of the packing forced against the wall of the bodyor of the shaft with which it is in sliding support contact.

Due to this concept of the actuator, the packing, in particular itsactive surface, is kept permanently against the surface with which thispacking is in sliding support contact in order to prevent any risk ofleaks and to compensate for premature wear of the packing.

Again, due to this pressurization of the packing in combination with thedesign of the packing that simultaneously ensures sealing between thechambers and sealing of the chambers to the outside, a perfect result isobtained that limits the risks of leaks to a significant degree.

The invention will be well understood by reading the followingdescription of embodiments with reference to the attached drawings inwhich:

FIG. 1 shows a partial diagrammatic view of a rotary actuator accordingto the invention in which the shaft of the actuator has been likewiseshown only in the left part of the figure;

FIG. 2 shows a perspective, side-to-side view of the packings with whichthe shaft and the body of the rotary actuator that is the object of theinvention respectively can be equipped;

FIG. 3 shows a perspective view of the packings that equip respectivelythe shaft and the body of the actuator in a position corresponding tothe installed state on said components;

FIG. 4 shows a partial perspective view of packing that can equip ashaft provided with two vanes arranged diametrically opposite oneanother on the axis of the shaft;

FIG. 5 shows a partial diagrammatic view of another embodiment of anactuator according to the invention;

FIG. 6 shows a partial perspective view of the packings that equip atleast one part of the actuator of FIG. 5 when these packings are notinstalled;

FIG. 7 shows a partial perspective view of part of the packing equippingthe actuator of FIG. 5 when these packings are installed;

FIG. 8 shows a transverse cutaway view of the actuator of FIG. 5 and

FIG. 9 shows a detailed view of the partition supported by the body ofthe actuator.

As mentioned above, the rotary actuator 1, the object of the invention,is composed of a body 2 and a shaft 3 that delineate a working volumebetween one another. Thus, in the example shown in FIG. 1, the actuatorcomprises only a single working volume, while the actuator of FIG. 5comprises two working volumes. Each working volume is composed of anannular cavity compartmented by at least two partitions 4, 5 extendingbetween the two surfaces 19, 20, the so-called end surfaces of saidcavity. One of these radial partitions 4 is supported respectively bythe shaft 3; the other shown at 5 is supported by the body 2 of theactuator. Thus, in the examples shown in the figures, the body 2 is aparallelepipedic body formed by the assembly of two half-shells in sucha way as to delineate, when the two half-shells are combined, a closedcylindrical cavity except for two passages at its ends allowing exit ofthe shaft 3 arranged longitudinally within the cavity that has thus beendelineated by the body 2. The shaft 3 and the body 2 thus form anannular cavity compartmented by at least two radial partitions 4, 5 orvanes. These partitions or vanes can have a large number of shapes. Inthe examples shown, they are composed simply of a plate that can beformed from a single piece with the element of the actuator that bearsit or can be connected to this element and fixed to the latterespecially by nesting. Thus, in the examples shown, the body 2 and theshaft 3 each comprise a groove that is intended to house a partitionwith one of its edges coming to rest within said groove. The opposite,free edge of the partition for itself is equipped with packing 6, suchas an elastically deformable seal. These partitions, by their free edgeand more particularly via the packing 6 that equips such a free edge,thus come into airtight, sliding support contact, one against the insidewall 2A of the body 2, the other, namely the partition 5 supported bythe body 2 of the actuator, against the outside wall 3A of the shaft 3.It should be noted that sliding support contact is defined as twosurfaces in support contact being moved by relative displacement. Thus,the active surface of the packing and the surface of the body or of theshaft against which the packing is supported are activated by relativedisplacement that generates this sliding support contact between saidcomponents.

Although in the examples shown, except for the packing of FIG. 4 thatcorresponds to that of a shaft equipped with two vanes, the shaft 3 andthe body 2 are equipped with a single vane, it is obvious that the shaft3 could be equipped with several vanes without departing from theframework of the invention.

Due to the arrangement of the radial partitions 4, 5, the latter thusform at least two chambers 7, 8 with variable volume within the annularcavity by interworking with the body 2 and the shaft 3 of the actuator.These two chambers 7, 8 are capable of being pressurized alternately, byintake of fluid, to generate a relative rotational displacement of thebody 2 and of the shaft 3. In the examples shown, the turning part ofthe actuator 1 is composed of the shaft 3, the body 2 being stationary.The reverse approach in which the turning part of the actuator 1 wouldhave been composed of the body 2, the shaft 3 being stationary, couldalso have been implemented in an equivalent manner. In the examplesshown, the intake of fluid used to feed the chambers 7 and 8 of variablevolume of the actuator 1 is done by the shaft 3. It could have been doneequivalently using the partition 5 that is integral with the body 2.Thus, the shaft 3 and/or the partition 5 integral with the body 2 of theactuator integrate(s) at least two lines 17, 18 that are usedalternately as the fluid intake and discharge line of the chambers 7, 8of the actuator to allow alternate pressurization of the chambers 7, 8.

The chambers 7, 8 thus alternately comprise a fluid intake chamber and afluid discharge chamber. When the rotary actuator 1 includes only asingle partition integral with the body 2 and a single partitionintegral with the shaft 3, it results in the possibility of driving theshaft 3 or the body 2 respectively over an angular range of roughly360°. Several partitions equipping respectively the body 2 and the shaft3 could have been provided in an equivalent manner. In this case, themovement of the component parts of the actuator 1 is limited to theinterior of the aforementioned angular range. It could also have beenenvisaged that the shaft of the actuator comprise the body of a second,similar actuator whose shaft would be located coaxially to the shaft ofthe first actuator and within the latter. This assembly would allowrotation over more than 360° with single or double control. Theoperation of a rotary actuator 1 will not be described in more detailbelow because it is well-known to those skilled in this art.

In a manner characteristic of the invention, each packing 6 that equipsthe free edge of a partition 4, 5 is extended in the direction of eachend surface 19, 20 of the annular cavity as far as said surface in orderto extend into the connecting zone between the end surface 19, 20 andthe body 2 or the shaft 3, respectively. This packing 6 that thus equipsthe shaft 3 or the body 2 is present in the form of a continuous linearseal that is not preformed and that is available in thousand meterlengths and can be cut to length, in order to come to rest in a grooveof the actuator that is shaped depending on the desired arrangement ofthe seal. This seal thus develops from one end surface 19 to the other20 following a loop trajectory, the closing of the loop being obtainedat least by the ends of the strip comprising the seal being brought intocontact. Initially this seal is preferably not preformed and can, ifnecessary, be shaped hot when the seal is being installed.

In this way, seals are obtained that correspond to the configurationsshown especially in FIGS. 2 to 4. It should be noted that the endsurfaces of the working volume can be composed either of supportedflanges positioned on the shaft, as shown in FIG. 1, or by the endsurfaces of the body 2, as shown by the ends of the body of FIG. 5,without departing from the framework of the invention. Regardless of theconfiguration adopted for these end surfaces, the packing extends justas far as these end surfaces to ensure a seal between the chambers withvariable volume and the outside. Thus, the same packing is used at thesame time for sealing chambers between themselves and for sealing thechamber to the outside without, however, complicating the configurationof this packing that has a form of a simple seal strip that is availablein thousand meter lengths and that can be cut to length. Thus, anyinventory of preformed seals becomes useless. Moreover, such a seal canbe replaced extremely easily since it is enough to reposition the sealwithin the groove of the body or the shaft of the actuator.

In the examples shown, this packing 6, at the level of the free edge ofeach partition 4, 5, has the form of two axial branches, in this caseparallel, extending from one end surface 19 to the other 20 so as toform a double sealing barrier.

In the examples shown, the closing of the loop formed by each packing 6that develops from one end surface 19 to the other 20 following a loopedtrajectory is obtained by simple overlapping of the ends of the stripcomprising the seal. The ends of the seal in this case, to facilitatetheir overlapping, are bevelled as shown in particular in FIGS. 2, 4 and6 in which the closing zone has been circled. This closing zone islocated at the level of the part of the packing that extends as far asthe end surfaces in the connecting zone between the shaft and the body.In the examples shown, these packings 6 of the shaft 3 and the body 2extend to the level of the end surfaces 19, 20 with respect to oneanother and are separated from one another by a connecting strip 21 suchas a collar or washer, comprising a sliding track of each of thepackings 6 and thus preventing packings 6 from rubbing against oneanother. Thus, in this embodiment, the end surfaces 19, 20 are composedof, for example, a supported flange of the shaft 3. The packings 6 ofthe body 2 and of the shaft 3 extend at the level of said surfaces intothe same plane orthogonal to the shaft 3. The packing 6 of the shaft 3is positioned on the periphery of said flange, preferably opposite thepacking 6 that equips the body 2 of the actuator. It is in thisconfiguration that the most efficient sealing is obtained. In theabsence of the connecting strip composed, in this configuration case, ofa collar, the packings would be led to rub against one another, thengenerating premature wear of the packing. To prevent such a phenomenon,a split collar is inserted between said packings. When the shaft 3 lacksthe supported flanges, the end surfaces are arranged at the level of thebody 2, as shown by one of the ends of the actuator of FIG. 5. In thiscase, as is shown in FIG. 7, the packings equipping the body 2 and theshaft 3 are routed into the connecting zone of the end surfaces betweenthe body and the shaft to be arranged in two parallel planes, theconnecting strip 21 being composed in this case of a washer 21 that isinserted between said packings for the same reasons as those mentionedabove.

According to the number of vanes of the shaft 3, the packing of theshaft 3 can conform either to that shown in FIG. 2 in the left-handview, or that shown in FIG. 4. Each time, this packing extends at leastover part of the circular periphery of the flange that is intended tocomprise one end surface before joining the other end surface by alinear portion following the free edge of the partition and thenreturning in the direction of the first end surface once this second endsurface is still equipped in the direction of the free side of thepartition.

In the example shown in FIG. 5, the shaft 3 of the actuator 1 isprovided somewhere over its length with at least one supported flange 15that is integral with the partition 4 that is carried by the shaft forthe purpose of limiting the risks of buckling of the latter. This flangedivides the body 2 into two working volumes, comprising one end surfaceof each working volume. The working volumes communicate with one anothervia openings 16 arranged in the flange 15. The presence of the supportedflange 15, on the one hand, makes it possible to stiffen the shaft inthe direction of length and to prevent sagging of the latter, and, onthe other hand, to integrate at least one transverse edge of thepartition 4 into said flange 15 in such a way as to limit the risks ofbuckling of this partition. Thanks to this solution, a longer actuatorcan be produced.

To complete the sealing of the assembly, the part of the packing 6turned toward the part of the actuator, such as the partition 4, 5, body2 or shaft 3 with which it is integral, can be subjected duringoperation of the actuator to a thrust force F that tends to keep theso-called active part of the packing 6 pushed against the wall of thebody 1 or of the shaft 3 with which it is in sliding support contact.The active part of the packing 6 is that which will come into contactwith a surface of the wall of the body 2 or of the shaft 3 to ensuretightness.

In the examples shown, the thrust force F is applied via pressurizedfluid that is brought into contact with the packing 6. This pressurizedfluid, brought into contact with the packing 6, is composed of the fluidthat feeds the chambers 7, 8 of the actuator 1. Thus, the pressurizedfluid that is intended to apply a thrust force F to the packing 6 feedsa chamber 9, the so-called pressure chamber of the packing 6 that isarranged between the packing 6 and the part of the partition 4, 5 orsupported flange or the body 2 that acts as the seat for this packing 6.This chamber 9 extends preferably over the entire length of the packing6.

To facilitate the application of such a support force, the packing canassume a shape corresponding to that shown in FIG. 9. In this case, thepart of the packing 6 turned towards the partition 4 or 5 has oneconcave surface with the concavity turned toward said partition ortoward the element of the actuator that bears it. The pressure chamber 9of the seal as for itself can assume the shape of a cylindrical cavity.

In the examples shown, the pressure chamber 9 of the packing 6 issupplied with fluid via a line 10, 11A, 11B that communicatesselectively with one or the other of the chambers 7, 8 of the actuatordepending on the pressure that prevails within said chambers 7, 8.

Thus, the thrust force F applied via the pressurized fluid is directly afunction of, or is controlled by, the pressure prevailing within saidchambers. It is the chamber with the highest pressure that feeds fluidto the pressure chamber 9 of the packing 6. Thus, this results in thatthe thrust force F applied via the pressurized fluid is the highestpossible due to the fact that it results from the fluid with the highestpressure within the actuator in the operating position of the latter.This fluid feed line from the pressure chamber 9 of the packing 6 isrouted into a partition 4, 5 of the rotary actuator 1 and into the endsurfaces 19, 20 of the shaft 3 or of the body 2. Thus, in the exampleshown, in particular in FIG. 8, each partition is provided with such aline. This line is composed of a first segment 11A, 11B that establishescommunication between the chambers 7, 8 of the actuator. This firstsegment of the line thus extends from one surface of the partition tothe other surface of said partition and comprises a line that crossessaid partition. This line thus extends essentially perpendicular to thelongitudinal axis of the shaft 3. This first segment 11A, 11B of theline ends in a second fluid feed segment 10 of the pressure chamber ofthe packing 6. This second segment 10 of fluid feed from the pressurechamber 9 is likewise perpendicular to the longitudinal axis of theshaft 3. However, it extends in the partition from the free edge to theopposite edge that is integral with the shaft or the body of thepartition. The first segment 11A, 11B that establishes communicationbetween the chambers 7, 8 of the actuator is equipped with a closingelement 12 that can move depending on the pressure prevailing within thechambers 7, 8 of the actuator. This element 12 thus in turn closes thepart 11A or 11B of the first segment extending between the chamber 7, 8of the actuator under pressure and the discharge 13 of this firstsegment into the second segment 10. Thus, in the example shown in FIG.8, the partition 4 that equips the shaft 3 is provided with a section11A of the line ending in the chamber 8 and a section 11B of the lineending in the chamber 7. When the chamber 8 is an intake chambersupplied with pressurized fluid, while the chamber 7 is placed at theoutlet, the portion of the line 11A is supplied with pressurized fluid.The closing element 12 that equips this section of the line is a ballvalve 14 whose ball 14 can move between two end positions extending oneither side from the discharge 13 of the first segment 11A, 11B into thesecond segment 10. Consequently, this ball tends to move in thedirection of the chamber 7 and to close the section of the line 11B toprevent the fluid contained in the chamber 7 from reaching the sectionof the segment shown at 10 in the figure. When it is the chamber 7 thatcomprises the intake chamber, the chamber 8 then comprising an outletchamber, reversed operation is observed, the ball 14 moving each timeunder the effect of the strongest pressure prevailing within one chamberin the direction of the other chamber to close the line of the otherchamber, thus preventing any feed of the pressure chamber 9 of thepacking 6 by the chamber with the weakest pressure. Thus, the packing isconstantly exposed to the highest pressure prevailing within saidchambers. This results in optimization of the support force applied tosuch packing and consequently optimization of the effectiveness of thepacking.

As shown in particular in FIG. 9, the closing element 12 that can movedepending on the pressure prevailing within the chambers of the actuatorto close in turn the part of the first segment extending between thechamber 7, 8 of the actuator under pressure, and the discharge 13 ofthis first segment into the second segment 10 can be equipped with tworadial elements that project through the inputs of the first segment toextend into the first or into the second chamber of the actuator. Theseprojecting elements comprise end-of-travel stops for the actuator in thevicinity of the end positions of said radial partitions. They thusprevent premature wear of said partitions.

In the embodiments in which the shaft 3 is provided on each of its endswith a supported flange, the pressure prevailing in the chambers isapplied to these flanges that themselves are contained within the bodyof the actuator. This results in a higher mechanical resistance of theassembly.

Due to the design adopted for each packing, the disassembly andreplacement of such packing can be done extremely easily. In the case inwhich closing of the loop is obtained by simple overlapping of the endsof the strip comprising the seal, it is enough to pull on one of theends and to remove all the packing from the groove, the body or theshaft in which it is seated until the seal is completely removed. Then,a new seal can be installed that will originate, for example, from aseal spool. This seal can be cut to length and thus promptly installedin the groove of the body or the shaft to allow the installation of newsealing.

1. Rotary actuator (1) of the type composed of a body (2) and a shaft(3) delineating between one another at least one working volume, eachworking volume being composed of an annular cavity compartmented bymeans of at least two partitions (4, 5) extending between two surfaces(19, 20), the so-called end surfaces of said cavity, one (4) of theseradial partitions supported respectively by the shaft (3), the other (5)by the body (2) of the actuator, these radial partitions (4, 5) by theirfree opposite edge equipped with packing (6), coming into watertight,sliding support contact, one (4) against the inside wall (2A) of thebody (2), the other (5) against the outside wall (3A) of the shaft (3),in such a way as to form at least two chambers (7, 8) of variable volumecapable of being pressurized alternately by intake of fluid to generaterelative rotational displacement of the body (2) and of the shaft (3),characterized in that each packing (6) that equips the free edge of apartition (4, 5) is lengthened in the direction of each end surface (19,20) of the annular cavity as far as said surface in order to extend intothe connecting zone between the end surface (19, 20) and the body (2) orshaft (3) respectively, this packing (6) that equips the shaft (3) orbody (2) being present in the form of a continuous linear seal that isavailable in thousand meter lengths and that can be cut to length, tocome to rest on the groove of the actuator that is shaped depending onthe desired arrangement of the seal, this seal developing from one endsurface (19) to the other (20) following a looped trajectory, closing ofthe loop being obtained at least by the ends of the strip comprising theseal being brought into contact.
 2. Rotary actuator (1) according toclaim 1, wherein the packing (6) at the level of the free edge of eachpartition (4, 5) has the form of two axial branches extending from oneend surface (19) to the other (20) so as to form a double sealingbarrier.
 3. Rotary actuator (1) according to claim 1, wherein theclosing of the loop formed by each packing (6) that develops from oneend surface (19) to the other (20) following a looped trajectory isobtained by simple overlapping of the ends of the strip comprising theseal.
 4. Rotary actuator (1) according to claim 3, wherein the ends ofthe seal are bevelled to facilitate their overlapping.
 5. Rotaryactuator (1) according to claim 1, wherein the packings (6) of the shaft(3) and the body (2) extend to the level of the end surfaces (19, 20)opposite one another and are separated from one another by a connectingstrip (21) such as a collar or washer, comprising a sliding track ofeach of the packings (6) and thus preventing the packings (6) fromrubbing against one another.
 6. Rotary actuator (1) according to claim1, wherein the end surfaces (19, 20) are composed of a supported flangeof the shaft (3), the packings (6) of the body (2) and of the shaft (3)extending at the level of said surfaces into a plane orthogonal to theshaft (3), the packing (6) of the shaft (3) being positioned on theperiphery of said flange, preferably opposite the packing (6) thatequips the body (2) of the actuator.
 7. Rotary actuator (1) according toclaim 1, wherein the shaft (3) of the actuator (1) is provided somewhereover its length with at least one supported flange (15) that is integralwith the partition (4) supported by the shaft for the purpose oflimiting the risks of buckling of the latter, this flange (15) dividingthe body (2) into two working volumes and comprising one end surface ofeach working volume, said working volumes communicating between otheranother via openings (16) arranged in said flange (15).
 8. Rotaryactuator (1) according to claim 1, wherein the part of the packing (6)turned toward a part of the actuator, such as the partition (4, 5), body(2) or shaft (3) with which it is integral, is capable of being exposedduring operation of the actuator to a thrust force (F) that tends tokeep the so-called active part of the packing (6) pushed against thewall of the body (1) or of the shaft (3) with which it is in slidingsupport contact.
 9. Rotary actuator (1) according to claim 8, whereinthe thrust force (F) is applied via pressurized fluid that is broughtinto contact with the packing (6), this pressurized fluid being composedof the fluid that feeds chambers (7, 8) of the actuator (1).
 10. Rotaryactuator (1) according to claim 9, wherein the pressurized fluid that isintended to apply a thrust force (F) to the packing (6) feeds a chamber(9), the so-called pressure chamber of the packing (6), which isarranged between the packing (6) and the part of the partition (4, 5)that acts as the seat for said packing (6), this chamber (9) extendingpreferably over the entire length of the packing (6).
 11. Rotaryactuator (1) according to claim 10, wherein the pressure chamber (9) ofthe packing (6) is supplied with fluid via a line (10, 11A, 11B) thatcommunicates selectively with one or the other of the chambers (7, 8) ofthe actuator depending on the pressure that is prevailing within saidchambers (7, 8).
 12. Rotary actuator (1) according to claim 11, whereinthe fluid feed line from the pressure chamber (9) of the packing (6),arranged in a partition (4, 5), comprises a first segment (11A, 11B)that establishes communication between the chambers (7, 8) of theactuator, this first segment (11A, 11B) ending in a second fluid feedsegment (10) from the pressure chamber (9) of the packing (6), the firstsegment (11A, 11B) being equipped with a closing element (12) that canmove depending on the pressure prevailing within the chambers (7, 8) ofthe actuator (1) in order in turn to close the part (11A or 11B) of thisfirst segment extending between the chamber (7, 8) of the actuator underpressure and the discharge (13) of this first segment into the secondsegment (10).
 13. Rotary actuator (1) according to claim 12, wherein theclosing element (12) is a ball valve (14) whose ball (14) can movebetween two end positions extending on either side from the discharge(13) of the first segment (11A, 11B) into the second segment (10). 14.Rotary actuator (1) according to claim 2, wherein the movable closingelement (12) is equipped with two radial elements that project throughthe inlets of the first segment to extend into the first or into thesecond chamber of the actuator, these projecting elements comprisingend-of-travel stops for the actuator in the vicinity of the endpositions of said radial partitions.
 15. Rotary actuator (1) accordingto claim 2, wherein the closing of the loop formed by each packing (6)that develops from one end surface (19) to the other (20) following alooped trajectory is obtained by simple overlapping of the ends of thestrip comprising the seal.
 16. Rotary actuator (1) according to claim 3,wherein the movable closing element (12) is equipped with two radialelements that project through the inlets of the first segment to extendinto the first or into the second chamber of the actuator, theseprojecting elements comprising end-of-travel stops for the actuator inthe vicinity of the end positions of said radial partitions.